Elizabeth Connell as Leonore and James McCracken as Florestan in Fidelio at the San Francisco opera house in 1987. Photograph: Ron Scherl/Redferns

The internationally acclaimed dramatic soprano Elizabeth Connell, who has died at the age of 65 of cancer, was a dedicated artist with a popular following who paced her career to perfection. Born in Port Elizabeth, South Africa, she studied in Britain at the London Opera Centre and made her debut as a mezzo-soprano at Wexford as Varvara in Kát'a Kabanová (1972).

Between 1975 and 1980 she sang regularly at English National Opera, tackling major roles such as Eboli in Don Carlos, Azucena in Il Trovatore, Donna Elvira in Don Giovanni and Judith in Duke Bluebeard's Castle. After singing Ortrud in Lohengrin and Brangäne in Tristan und Isolde at Bayreuth (1980-82), she made the switch from mezzo to soprano in 1983, following which she took on a wide range of challenging roles including Fiordiligi in Così fan tutte, Marie in Wozzeck, Elisabeth in Tannhäuser, Leonore in Fidelio, Norma, Senta in The Flying Dutchman and Ariadne. Then, just as she might have been expected to begin to wind down, she blossomed in her 60s in immensely taxing roles such as Turandot and Elektra, her voice sounding as youthful as ever.

Benefiting from her own research into the history and technique of singing and a shrewd management of vocal resources, she continued to give audiences immense pleasure with her fresh, intelligent, often thrilling performances. At a solo recital at St John's Smith Square, London, in November 2010, she delivered an amusing self-deprecating diva's farewell, written for her by Betty Roe: "When a diva says she's going/There's no earthly way of knowing/Just how long her going's going to protract."

Retirement at that point was not in fact her intention: she was bidding farewell to Britain only to take up more engagements in Australia. Sadly, illness intervened the following year and she died back at her home in Richmond-on-Thames, displaying to the end her sly wit and indomitable spirit.

She first came to Britain in 1970 and studied with Otakar Kraus, rapidly making a reputation for herself in Britain and Australia. The years 1975 to 1980, when she sang a number of mezzo roles with ENO, were a golden period for both her and her many London fans. Particularly outstanding in these years were her girlish, almost flirtatious Sieglinde (Die Walküre), an intensely moving Waltraute (Götterdämmerung) and a stunning Eboli, while the youthfulness of her tone offered new insights into the roles of Amneris (Aida) and the Kostelnicka, the churchwarden's widow (Jenufa). In the Italian Girl in Algiers she displayed impressive coloratura and an unexpected comic gift.

She also made her Covent Garden debut at this time as Viclina in I Lombardi (1976). It was during her three-year stint at Bayreuth at the start of the 1980s that she began to realise that low-lying roles such as Kundry (a part she was covering) were not suitable for her. Reinventing herself as a dramatic soprano, she graced the major international stages – including La Scala, the Metropolitan, Munich, Hamburg, Glyndebourne, Vienna and San Franciso – with a succession of roles in which she demonstrated flawless diction, a dynamic stage personality that verged on the hyperactive and above all an engaging vocal quality.

Her recordings included Guillaume Tell under Riccardo Chailly, Mahler's Symphony No 8 under Klaus Tennstedt, Franz Schreker's Die Gezeichneten under Lothar Zagrosek, Schubert lieder with Graham Johnson, operatic scenes by Wagner and Strauss under Muhai Tang, and Owen Wingrave under Richard Hickox. Her 1997 recording of the role of Isolde under Eve Queler demonstrated both her burnished, jewel-like tone and a legato line made up of animated phrases alert to text. The character's anger and sarcasm in Act I were conveyed through biting consonants and tonal colouring rather than weight of voice; the Liebestod too was characteristically infused with humanity.

Over a decade later, by which time she was 62, Connell delighted audiences yet again with her Turandot at Covent Garden (a role she had taken previously in Hamburg, Prague and with Opera Australia). Here once more her voice sounded astonishingly youthful, yet was also notable for its warmth and generosity – a welcome change from the steely tone traditionally evinced by the ice princess. The character she projected was still formidable but also touchingly vulnerable.

She is survived by her three brothers, John, Peter and Paul, and her sister, Rosemary.

• Elizabeth Connell, opera singer, born 22 October 1946; died 18 February 2012